Keyed radio beacon



March 2, 1948. L. A. DE ROSA l KEYED RADIO .BEACON Filed Deo. 6, 1943 3 Sheets-Sheet 1 IN V EN TOR.

UAQQQQ Nu A A T TRNEY March 2, 194s.

l.. Af DE ROSA 2,436,796

KEYED RADIO BEACON Filed Dec. 6, 1943 3 Sheets-Sheet 2 To P04756 or Mom/AMS ma Pon/5A March 2, 1948. A. DE OSA* KEYED RADIO BEACON Filed Dec. 6, 1943 /ffYE/P ro fwrfMx/A sw/rcf/ 19 To ATE CONTROL SUPPLY DUNE 1 SOURCE 5 Sheets-'Sheet 3 INI-'ENTOR UU/5 A. DE F054 /H'YUHNHY l Patented Mar. 2, 1948 T QFFEC KEYED RADIO BEACON Louis A. De Rosa, West Brighton, Staten Island,

N. Y., assignor to Federal Telephone and Radio Corporation,-New York, N. Y., a corporation of Delaware lApplication December 6, 1943, Serial No. 513,097 19 Claims. (Cl. Z50- 11) This invention relates to radio beacons and more particularly to equi-signal radio beacons of the keyed pattern type.

A common type of radio beacon for use with aural indicators ls one inv which radiation patternsare caused to overlap to deiine a guiding zone. VThe patterns carry separate signals, preferably keyed to produce an interlock, such as may be obtained from the Morse letters A and N. At points along the.; chosen Vcourse the two signals merge but, upon 'departure from course, one of the letters tends to predominate.

' The human` ear is `provided with certain mechanisms which operate to adjust the perception level of sounds in response to the general sound level received. Upon a change in volume level the ear tends to `adjust itself to the new sound intensity. This action is not instantaneous but takes an appreciable time in the order of 50-60 milliseconds. During this period of change in the hearing mechanism, the response is more nearly linearV than at `other times. As a conse-v quence, the perception of dierence in sound levels is more acute during this period than at other periods.

In accordance with these principles of aural response, it is an object of my invention to provide a keyed signal translator and method in which aural distinction between two signals may be improved.

It is a further object of my invention to provide a comparison translator of the keyed signal type in which the beginning and end of each signal element is caused to increase above the normal level of the signal, thus greatly increasing the perception, while increasing the power level of the entire system onlyslightly.

In accordance Awith a feature of my invention, I provide amplitude control means operative with a keyer of an aural radio beacon or keyed comparison receiver to increase the energy level of each signal element at the beginning and ending thereof. The rate of increase of `energy level is preferably made as rapid as possible in order to maintainV arelatvely low average power consumption of the system. `The increase, however, must be sufliciently gradual toV permit the human ear to adjust itself to the increased power level, preferably. taking place over a period in the order In positions where the signals are of equal amplitude the ear does not perceive any variation between the signals being compared. Upon departure from this position of signal equality, however, the two signals are compared. atthe increased'energy level, occurring while the ear is in its more sensitive condition. As a consequence, departure from signal equality position will be more readily perceived. l A better understanding of my invention and the objects and features thereof may be had from the particular description of certain embodiments thereof made with reference to the accompanying drawing, in which: Fig. 1 is a schematic circuit diagram of a radio beacon embodying the features of my invention;

Fig. 2 is a set of curves illustrating the operation of a radio beacon in accordance with my invention; Y Y

Fig. 3 is a modified keying and control mechanism for use in a beacon circuit in accordance with my invention; I

Fig. 4 is a further modified keying arrangement using cam keying in accordance with my invention;

Fig. 5 is a still further modification of a keying mechanism using a slow operating relay; and

Fig. 6 is an illustration of my invention ap-v plied to a comparison receiver apparatus.

Turning rst to Fig. 1, I0 represents a radio frequency source and I I a tone frequency source, the outputs of which are combined in modulator I2 to produce a tone modulated radio frequency output. This modulated energy is applied over power amplifier I3 to a radio beacon antenna system illustrated generally at I4. In the illustrated circuit, this beacon antenna system comprises a central radiating antenna I5 and two side radiators I 6, I 6A. The antenna system is adapted to produce a directive radio beacon pattern, the direction of which is changed alternately through the operation of keyer I .'I, keying relay coil I 3 and relay switch I9. y Operationoi switch I9 serves to reverse the phase of the enfergy supplied to antennas I6 and IBA producing alternately shifted radiation patterns effectively overlapping in space thereby defining `a radio beacon course. It should be understood that other types of radio Ybeacons may be provided, if desired, in which case switch I9 will serve to make other connections to produce the alternately keyed ra'- dio beacon. For example, the common crossed loop beacon, or the keyed reflector type of beafcon, may be used.

The structure, so far described, may be considered as a known form of aural radio beacon. In accordance with my invention, I provide a control circuit 20 operated in synchronism with keyer I'I to produce in the output oi power amplier I3 an increased energy effect at the time Yshaping circuits to produce reversing switch I9 is operated. Thus, at the end and at the beginning oi each signal element, the energy level is increased providing a greater contrast in signals upon departure from the course by a craft. In the arrangement illustrated in Fig. l, plate potential for tubes 22 of power amplifier I3 and for modulator l2 is supplied from source 23 over choke coil 24, resistance 25 and lead lines 26 and 21 to the respective circuits. This plate potential is sufiicient to produce the normal amplitude of the modulated radio frequency energy supplied to antenna I4, At every operation of keyer l1 energy of the keying wave i' is supplied to differentiator 28 which serves to produce potential peaks at the beginning and end of each applied signal element. lIhese peaks, however, will be reversed in phase with respect to one another. tiator 28, the peaks areY supplied over clipper 29 and clipper inverter 38 across the resistance 25. Clippers 29 and 30 are preferably provided with pulses having a sharp leading edge and a sloping, trailing edge and pulses having a sloping, leading edge and sharp trailing edge, respectively, for application across resistance 25 at the beginning and end of each signal element caused by operation of switch i9. Thus, a potential of the desired form is applied in series with the energy from source 23 to the plates of power amplifier I3 and modulator I2 simultaneously with the switching operation of switch I9. The output signals produced may ac cordingly have form as shown more clearly in the curves of Fig. 2.

In Fig. 2, curve a represents the tone modulated carrier frequency signalv impulses, resulting from the switching operation, observable on a craft which is directly on course, The elements marked N represent the Morse letter N corresponding to one keying position of switch i9 and the portions marked A represent the signal elements of aninterlocking Morse letter A produced from the other keying position of switch I9. The normal signal level is represented at 3l. The increased energy level at the initiation or beginning of each signal element is represented by the sloped portions 32 and the increased energy at the trailing edge of each signal element is represented by the sloped portions 33. When a craft is oif course, the received modulated radio frequency energy will be in the form represented by curve b of Fig. 2. The portions N of the signal are relatively increased in amplitude while the portions A are relatively decreased in amplitude. As a consequence, at the instant of keying, there is present a difference in signal level represented by the portion 34. The percentage difference in level ofy the two signals is determined by the degree of departure from course. The absolute difference in signal level, however, because of the peaking of the energy at the beginning and end of each signal element is increased over difference at the average signal level which would be present were this func tion eliminated. The sensitivity of the ear will be increased at the time of switch-over, because of the change brought about by the increase in energy level. As a consequence, the difference in signal upon departure from course is accentuated and departures may, therefore, be more readily determined. In every case slopes 32 and 33 should be made to rise and fall as rapidly as possible for the purpose of conserving energy. The change must, however, be sufficiently gradual to permit the human ear to adjust itself tothese From the output of differen-A 4 variations in energy level. In this way, the ear will build up to a higher relative sensitivity enabling perception of the difference in energy levels to be increased.

The demodulated signals shown in curve b are illustrated in curve c of Fig. 2, showing the audio envelope that' willbe' applied to the ear in operation of the system in accordance with my invention.

-While the circuit shown in Fig. 1 will operate to produce the desired results, a simpler circuit arrangement for producing the desired effects is vshown in Fig. 3.. In this figure, keyer I1 is shown invk detail as a cam mechanism 4l) having raised portions 4| and 41A and depressed portions 42, 42A cooperating with a switch arrangement 45, 41, serving alternately to complete and to break the `circuit from battery 35 through relay coil I8 to ground 49. Alternate energization and deenergization of coil I8 serves to operate the switching mechanism, such as I9 shown in Fig. l. Connected in the supply line to plate circuit leads 26 and 21 is a condenser 43 coupled to ground at 49 and shunted byV resistor 44. The shunt, or parallel, connection of resistor 44 may be interrupted at a pair of contacts 46 and 48 which cooperate the 'contact 45. When contact 45 is closed against either of the contacts 46 or 48, the normal plate potential is supplied to lines 26 and 21. lThe shunting effect of resistor 44 holds this potential `at a predetermined level below that which wouldl be present if no resistor were'provided. Upon rotation ofcam 40, contact 45 is raised, breaking its. contact with 46 and removing the resistance element from its connection to ground. As a consequence, the plate voltage starts to rise, charging of condenser 43 serving to control the rate of build-up. The potential supplied lines 26 and 21 thus increase as shown at 32 in curve a.

The slopes of raised cam portions 4I, 4IA are preferably made relatively gradual so that the condenser maybe fully charged before resistor 44 is again connected in shunt to the condenser. Contact 45 is arranged to next make contact with contactor 41 causing relay I8 to operate and directionally shifting the antenna patterns. Upon further raisingof contact 45, it also closes a circuit to contact 48, again connecting resistance 44 to ground. The increased potential caused by the disconnection of resistance 44 then gradually leaks off so that the plate potential applied to lines 26 and 21 returns to normal.

Upon further rotation of cam 4U, contact 45 rst breaks contact withY contactor 48, disconnecting resistor 44 from ground, then breaks contact with contactor 41 (le-energizing relay I8 and operating switch i9 to its other position and then makes contact with contactor 46 reducingv the potential supplied to lines 26 and 21 in the same manner as described above. Thus, this simple mechanism serves to produce the desired wave form, as shown in Fig. 2 of the drawing.

-In` Fig. 4 is shown an arrangement substantially similar in operation to the form illustrated in Fig'. 3. However, in this arrangement, separate contactors 5B, 51 andv 58 are provided to cooperate with the separate contact elements 46, 41 and 48, respectively. Likewise, these contactor elements are provided with gradually sloping cam rider surfaces so that the raised portions 4l and 41A of cam 40 need not be made gradually sloping, as inthe case of Fig. 3. It is clear that this principle could be applied to the cam arrangement of Fig. 3, if desired', in place of that sag-soiree? as shw'n and likewise thesloping edgesof cam portions lIII if desired.

\ In Fig. 5 is illustrated a still further embodiment of the keying mechanism wherein the op-l eration of the switching elements is controlled by alslow operating relay mechanisms. In this ligure, relay I 8 is provided with an armature 50 and a dash pot 5I serving to cause the armature to respond slowly to operation of relay I8. Lines 2I and 2IA are connected to separate contactor elements ISAV to I SE, as

shown, and separate contactor elements 45A and and I9E, respectively, reversing the connections between lines 2| and 2IA. The operation period ismade sufficiently long to permit the building up ofpotential on lines 2G and 21. As armature E9 is moved further, contact 45A is closed against contactor 41, again connecting resistor 44 in parallel with condenser 43 and permitting the potentialjin leads 26 and 21 to return to normal. Upon de-energization of relay I8, the reverseV operation of the switch mechanism occurs, producing a similar type of operation in the circuit together with the reversal of the antenna keying.

While I have shown my invention 'applied to radio beacons, it is clear that the principles thereof apply to other translator systems as well. ,For example, the mechanisms shown in Figs. 1 and 3-5 may be applied to a receiver such as shown in Fig. 6. The antennas such as shown in Fig. 1, for example, may be used for reception, the directive patterns being switched alternately to provide overlapping reception patterns. The` received energy is applied to receiver 60, the output of which is coupled to an aural indicator 6I. When the antenna is aligned with a transmitter source, the reception patterns will produce equal intensity signals in the indicator. Control circuit 20 operated With keyer I1 serves to increase the amplitude output of receiver 60 at the time of switching to provide Vcomparison signals, as shown in Fig. 2, for example. It should be clear that the other forms of switching andkeying mechanisms may likewise be applied to the receiver of Fie. 6.

My invention is likewise applicable to any type of translator and indicator system in which comparison or contrast of signal conditions is desired, as Well as in radio transmitter and receiver systems.

It is clear that other forms of relay circuits may be used, if desired, and various forms of keying operationsmay be used. Furthermore, to those skilled in the art,it will be apparent that there are many types of circuit arrangements and operations which may serve to accomplish the results in accordance with my invention. While I have described specific embodiments of my invention and various modifications thereof, this description should not beconsidered as a limitation on my invention, as set forth in the objects thereof andin the accompanying claims.

and4IA couldv be applied to Figi 4,

I8 instead of by cam K in a predetermined space to 150i I to produce radiation lapping a predetermined zone in space to provide a 6'? whatisciaimeois: if* i 1. A directive radio-system comprising an ent ergy translator, a directive 'antenna means, -ke'y- Iing means for alternately coupling said trans` lator to said directive antenna 'means in different energy transfer relationship for 'predetermined' intervals to providel radiant action over patterns alternately overlapping a predetermined zdneflnA provide a direction indication, and means responsive to each operation of said keying means for increasing the amplitude levelof-said energy applied to said antenna means atV thev beginning and end of each of said intervals) v 2. In a radio directive system in which connections from an energyl translator to an an tenna' are alternately switched to provide alter` nately overlapping radiant action patterns, providing signalsv defining directive indication, an` arrangement for increasing the sensitivity of the aural comparison of the signals comprising a parallel resistance condenser circuit, switch means operative with the alternately switched connections for disconnecting said resistance from the circuit to increase the energy level to a predeter- I mined value above normal prior to switching said connections and forreconnecting said resistor in parallel to return -said circuit to normal after switching of said connections.-

3. A radio beacon comprising an energy solirce,

directive antenna meanak'eying` means for alternately applying energy from said source to said directive antenna' means in different energy transfer relationship for predetermined intervals patterns alternately overbeacon course indication, and means responsive to each operation of said keying means for increasing the amplitude level of "said energy applied to said antenna means'at the beginning' and 'end of 'each of said intervals. 4. Ina radio beacon in which connections from an' energy source to an antenna are alternately switched to provide alternately overlapping ra' diation patterns, providing signals defining a.

course in space, an arrangement for increasing the sensitivity of the aural comparison of the signals, comprising means for relatively gradually increasing vthe energy level to a predetermined' level abovenorm'al prior to said switching action."

' and means for relatively gradually decreasing said energy level to vnormal after said switching action. Y f 5.' In a radio beacon in which connections from' n an energy source to an antenna are alternately switched toprovide alternately overlapping radiation patternsj.' providing signals defining a course in space," an arrangement for increasing the sensitivity of the aural'comparison of the signals comprising a parallel resistance condenser circuit, switch means' operative with -the alternately switched connections for disconnecting said resistance from circuit to increase the energy level to a predetermined value above normal prior to switching said connections and for reconnecting said resistor-in parallel to return 'said circuit' to normal after switching of saidv connections.

6. VIn a radio beacon'in which connections from anenergy source to an 'antenna are alternately switched -to provide alternately overlapping radi'ation patterns, providingsignals dening a course'in space, the method of increasing the sensitivity of the aural comparison of the' signals comprising 'relatively gradually increasing the energy level to a predeterminedlevel. above nor#4 mal'prior to said switching action, and relativelyA- asse-ave 7. gradually decreasing said energy level` tok normal after said switching action. I

7. In a. directive radio-receiver system in which connections from a, radio receiver to an antenna are alternately switched to `provide alternately overlapping reception patterns, providing signalsv defining a direction line,the method of'increasingthe, sensitivity of the aural comparison of the signal comprising relatively gradually increasing they energy level to a predetermined level above normal prior to said switching action, and relatively gradually decreasing said energy level to normal after said switching action.

8l A radio beacon comprising a tone frequency source, av radio frequency source, a modulator for modulating energy from said radio frequency source with energy from said tone frequency source, a directive radiating means, means for applying energy from said modulator to said directive radiating means, keyer means for alternately altering the energy transfer to said radiating means to provide radiation patterns differu ing in directive characteristics and identified by separate signal elements to produce a zone of overlap defining a course in space, supply means for energizing said modulator normally to produce modulated energy of a given leveland means operative with said keyer means for altering said supply means to increase the energy level of said modulated energy above said given level for a short period overlapping in time the operation period of said keyer means, whereby the amplitude ofsad signals is. increased above said given level at the beginning and the end of each of said signal elements.

9. A radio beacon comprising a tone frequency source, a radio frequency source, a modulator for modulating energy from said radio frequency s ource with energy from said tone lfrequency source, a directive radiating means, means for applying energy from said modulator to said directive radiating means, keyer means for alternately altering the energy transfer to said radiating means to provide radiation patterns. differing in directive characteristics and identified by separate signal elements to produce a zone of overlap delining a course in space, plate supply means of a predetermined potential for said modulator. nor.. mally assuring a given output level of said modulated energy, and means operative with said keyer for increasingv said predetermined potential to a predetermined higher value for a period overlapping the operation period of said keyer means, whereby the amplitude of said signals is increased above said given level at the beginning and end of each. signal element.

l0. A beacon according toclaim -9, wherein said last named means comprisesa condenser and resister normally connected in shunt with said supply means and saidy last named means comprises a switch means in said resistor connection, and means for opening said switch means prior to operation of said keyer, and for closing said switch means after operationof said keyer, to remove the shunting eiect ofy said resistorv during operation of' said keyer.

11. A radio beacon comprising a. tonefrequency source, a radio frequency sourcel a. modulator for modulating energy from said radio frequency source with energy from said tone frequency source, a directive radiating means, means for applying energy from said modulator to said directive radiating means, keyer means vfor alternately altering the energy transfer to said radiating means to provide radiation patterns difforme in ai)v ' said resistor during operation of said keyer.

directive characteristics 'and identified by.. separate signal elementsto produce a zone of'ove'ilap defining a course in space, a keyer cam for operating said keyer means, and means operated by said cam for altering said supply means to increase the energy level of said modulated energy above said given level fora short period overlapping in time the operation period of said keyer means, whereby the amplitude ofr said signals is increased above said given level at the beginning and the end of each of said signal elements.

12. A beacon according to claim 11, wherein said last named: meanscomprises a condenser and resistor normally connected in shunt'with said supply means,V and said last named means comprises a switch means in said resistor connection., and means controlled by said cam for opening said switch means prior to operation of said keyer, and for closing said switch means after operation of said keyer, to remove the shunting effect of 13. A radio beacon comprising means for producing a tone modulated radio frequency carrier, a directive radiating means, means for applying said carrier to said radiating means, keyer means for alternately shifting the radiation axis of said radiating means to provide a course indication by comparison of venergy from said twopatterns, supply means for normally maintaining said car,- rier at a predetermined amplitude level, resistor, condenser means coupled in parallel t0 said supply means, and switch, means operative with said keyer means to open they circuit of said resistor immediately prior to, operation of said keyer means and to reclose the'circuit of said resistor after operation of said keyer means, whereby the amplitude level of said carrier will be increased during operation of said keyer.

14. A radio beacon according to claim 13, wherein said keyer means comprises an electromagnetic relay, and said switch means comprises switch contacts operative under control of said relay.

15. A comparison signal indicator, comprising a translator, means for alternately applying interlocking series of impulses to said translator, an audio indicator in the output of said translator for aurally comparing said series of impulses, and means for increasing the energy level of each of said impulses at the beginning and termination thereof, to increase the sensitivity of said comparison. A

16. In a comparison signal indicator in which aural comparison of an interlocking series of impulses is made, the method of increasing the perceptive sensitivity -of said comparison comprising increasing the amplitude level of each impulse at the beginning and end thereof, whereby the ear will have increased. sensitivity at the junction points of successive impulses.

17. A directive radio system comprising an' energy translator, a directive antenna means, keying means for alternately coupling said translator to said directive antenna means in different energy transfer relationship for predetermined intervals to provide radiant action over patterns alternately overlapping a predetermined zone in space to provide a direction indication, and means responsive to each operation of said keying means. for increasing the amplitude level of said energy applied to said antenna means for a period juxtaposed in time to the common time limit of said intervals.

18. A comparison signal indicator, comprising a translator, an audio indicator in the output of said translator for aurallyvcomparing said impulses, and means for increasing the energy level of an impulse occurring substantially at the common time limit of the interlocked impulses to increase the sensitivity of said comparison.

19. In a comparison signal indicator in which aural comparison of interlocking' impulses is made, the method of increasing the perceptive sensitivity of said comparison, comprising increasing the amplitude level of the impulses occurring substantially at the common time limit of said impulses whereby the ear will have inw Number The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date 2,157,677 Runge May 9, 1939 2,299,388 Hansell Oct. 20, 1942 

